In an electron probe microanalyzer (EPMA) using a wavelength-dispersive spectrometer (WDS), the specimen, the analyzer crystal, and the spectrometer are required to be placed on the Rowland circle at a higher accuracy so as to satisfy the focusing conditions for x-ray detection than in an electron probe microanalyzer employing an energy-dispersive spectrometer (EDS). Of the specimen, analyzer crystal, and spectrometer, a detection system comprising the analyzer crystal and spectrometer is moved by an integral mechanism. However, the specimen stage on which the specimen is placed is moved horizontally and vertically, tilted, and rotated independent of the detection system, because the stage determines the position on the specimen to be analyzed. This function of moving the specimen stage independent of the detection system is required not only in x-ray analysis but also in SEM involving specimen surface morphology observation and elemental analysis making use of reflected electrons.
When an x-ray analysis is made, a point or region to be analyzed is determined with an SEM image or the like. Then, the x- and y-coordinates of the specimen stage and its height are adjusted so that an arbitrary analysis point within this analyzed region is brought to a point where the focusing conditions are met, i.e., an analysis point. At this time, the alignment in the direction of the height of the specimen stage is often made, using an optical microscope.
Analyses using an electron probe microanalyzer are classified into (1) point-by-point analysis in which an analysis is performed whenever a point is selected appropriately and (2) mapping analysis in which a set of points is established within an analyzed region and the points are sequentially analyzed automatically. In the case of the point-by-point analysis, whenever a point is selected, the height is set. On the other hand, in the case of the mapping analysis, there exist a number of points to be analyzed. Therefore, it is difficult to set the height at every point because of complexity of the work and because it takes a long time to perform the work.
Accordingly, it is common practice to adopt the following technique. It is assumed that the whole specimen surface is flat and smooth. The heights, for example, of the specimen at the four corners are measured. The tilt of the specimen surface is found. The heights of every analysis point used for a mapping analysis are established, taking account of the tilt. In this way, if the specimen has a flat and smooth surface as a whole, an accurate analysis can be performed. However, it is sometimes necessary to make analyses of specimens having greatly uneven surfaces. If the heights used for the analysis are determined by the aforementioned method, the height may differ among the analysis points because of the unevenness. Therefore, in the case of a specimen having a rough surface, the focusing conditions are not satisfied according to the analysis point. Consequently, sufficient x-ray intensities may not be obtained.
Therefore, where a mapping analysis is made of a specimen having a rough surface, the rough surface is smoothed by a polishing operation using feather cloth prior to the analysis. However, in practice, there exist numerous specimens which cannot be smoothed. If such a specimen incapable of being smoothed is analyzed with an electron probe microanalyzer without sufficient care, then an elemental distribution deviating from the actual distribution may be observed. In this way, there is the possibility that the analysis results in serious errors.
With respect to specimens having steps, the focusing conditions may not be satisfied, in the same way as in the case of specimens having rough surfaces. Hence, sufficient x-ray intensities may not be produced.
Where mapping analyses are performed by the prior art techniques in this way, it is difficult to perform accurate analyses of specimens having uneven surfaces, i.e., having irregularities and steps.